A variety of psychophysical, physical, electrophysiological, pupillographic and other tests are applied to normal and abnormal eyes to elucidate fundamental properties of normal vision, dark and light adaptation, color vision, color blindness and night blindness. The role of rhodopsin and cone visual pigments in such abnormalities is being elucidated, with the aid of biophysical measurements in vivo of the kinetics of their bleaching and regeneration with a retinal densitometer.